Electrical apparatus



Sept. 8, 1953 J. H. MAYFORTH ELECTRICAL APPARATUS Filed Sept. 29, 1949 INSULA'HON INVENTOR. 04% BY 9 W 00% Cl. 64am ATTORNEY.

Patented Sept. 8, 1953 ELECTRICAL APPARATUS John H. Mayforth, Queens Village, N. Y., assignor to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application September 29,1949, Serial No. 118,637

Claims. (Cl. 307-132) This invention relates to electrical apparatus and more particularly to an electrical circuit and device for providing interrupted current flow to apoint of use, such as to a transformer.

One of the objects of the present invention is to provide novel means ina circuit of the above character whereby substantially constant output may be obtained from a source of variable voltage.

Another object of the invention is to provide a novel spark generating or ignition circuit wherein the voltage at the sparking device is maintained substantially constant or within relatively narrow limits independently of voltage variations at the source of energy.

Afurther object is to provide novel means for automatically controlling the length of the interval during which the contacts of a vibrator are engaged.

Still another object is to provide a novel vibrator wherein the contact dwell is controlled in a predetermined manner in accordance with varia tions in the voltage available at the source.

A still further object is to provide an ignition system for combustion engines or the like wherein the supply of energy to the ignition coilis controlled to provide adequate sparking at var'ia'- ble supply voltages without danger of overheating' the coil.

Another. object is to provide a novel current interrupter with a variable dwell oontactorfor a special circuit in combination with a contactor which may have a fixed or variable frequency'for operating the interrupter.

Still another object is to provide novel apparatus for varying the period of current flow in an intermittently interrupted circuit While maintaining reasonably constant or within reasonably predetermined limits the frequency of operation of the circuitinterrupting means.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expresslyunderstood, however, that the drawings are for the purpose of illustration only, and are not intended to define the limits of the invention, reference for this latter purpose being had primarily .to the-appended claims.

In the accompanying drawing the single figure is a diagram of a device and electric circuit embodying one form of the present invention.

A single embodiment of the invention is diaway of example, in the form of a circuit adapted for use as an ignition system on internal combustion engines or .on so-called jet or turbo-jet engines, but it may also be used for numerous other purposes where intermittent electrical sparks are required or where a relatively constant intermittent output is desired from a variable supply voltage. In the circuit shown, the source of electrical energy is in the form of a battery l0. During normal operation of an engine ignition system embodying, by way of example, av standard 24 volt battery of the type now available, the source voltage for spark plug operation will vary fromv approximately 9 volts to 29 volts. In such systems now known wherein the current flow to a transformer is periodically initiated and interrupted by a magnetically operated vibrator, the voltage variations at the source result in a material variation in the output of the transformer and, hence, in the voltage across the spark gap. Under such circumstances, the system must be designed to provide ample output at the lowest voltage and this results in difficulties and undesirable consequences, such as overheating of the transformer coil, ineflicient operation, increased weight, decreased operating life, and many others.

The present invention comprehends novel meansfor obviating the above disadvantages of known systems by automatically varying the duration of current flow to the transformer or other load during each cycle of operation of the vibrator in accordance with the variations in source voltage. In the form of device shown, this result is accomplished by varying the dwell ofv the vibrator contacts I2 and M which intermittently close and open the circuit from source [0 to the transformer. The latter circuit comprises a manually operable ignition switch It, a reed I8 which carries contact l2, contact I4, a reed 20 on which the latter contact is carried, and the primary winding 22 of a transformer. Reeds l8 and 20 are electrically conductive and resilient. The return path from the primary winding to the battery may be through ground. The secondary winding 24 of the transformer is connected in serieswith an energy consuming load, such as a spark gap 26 which may be in the form of a spark plug or the like in a combustion o chamber'of an engine.

For periodically moving contact [2 into circuit closing engagement with contact [4 to thereby complete the circuit to the transformer, there is provided suitable electromagnetic means here grammatically illustrated in the drawing, by 66 shown in the form of a coil 28 with a magnetic core 30 to which is connected a pole shoe 3 l. Coil 28 is normally connected in circuit with battery III, when switch I6 is closed, through the normally closed contacts 32 and 33 which are carried by electrically-conductive, resilient reeds 34 and 35, respectively. One end of coil 28 is connected to reed 34 by a lead 36 and the other end is connected to the battery through ground. The circuit is completed by a lead 3! connecting reed to the other side of the battery through switch I6.

The upper end of reed I8 is provided with an armature or shoe 38 which is electro-magnetically caused to move to the dotted line position illustrated when coil 28 is energized. The inherent resiliency of reed I8 maintains it in the full line position against a stop 33 when coil 26 is not energized. Stop 39 is preferably mounted on a resilient reed 40 similar to reed 35 which functions as a yieldab le stop also for contact car rying reeds I8 and 20 when the latter move to the dotted line positions shown. When reed I8 is flexed to the right by theelectro-magnet, contact I2 engages contact I4 whereupon reed 20 is flexed to its dotted line position. Just before reed 20 reaches such position, a button 4| on said reed engages a button 42 on an upwardly extending portion of reed '35- to thereby flex the latter to its dotted line position and disengage contacts 32 and 33. The circuit to coil 28 being thus broken, said coil is deenergized and resilient reeds I8, 20 and 35' are permitted to return to their norm-a1 full line positions shown, thereby disengaging contacts I2 and I4 to interrupt current flow to primary winding 22 and re-engaging contacts 32 and 33- to again complete the circuit through coil ZB-and initiate another cycle of operation. The frequency of these cycles may be maintained nearly constant within a relatively small range by selecting suitable reeds and providing suflicient ampere turns on coi1 28 to make the saturation of core 30 at the lowest available voltage about the same as it is at the highest available voltage. It maybe desirable to vary this frequency somewhat indirect relation to the variations in source voltage to there' by supplement the functioning of this device by reducing the contact dwell at high voltages.

The ou'tputof transformer 22,24 depends'upon. the magnitude of the current in the prima'ry winding when the circuit is interrupted at con tacts I2, I4. While the circuitis closed, the time required for the current flowing through inductance 22 to reach a selected value or magnitude is dependent upon the available voltage at the sourcethe lower the voltage the greater the time required. In known systems of the'charac'- ter illustrated the available voltage at battery III varies rather widely for the reasons, among others, that energy from the battery is used for operating a starting motor and other purposes, the increased voltage drop within the battery upon any increase in the current now, and the speed of the charging generator varies with engine speed.

Since the available voltage at battery I0 for building up a flow of current in winding 22 may be variable for the reasons given above and others, novel means responsive to said voltage are provided for determining and varying the in-' terval or portion of the stroke during which contacts I2 and I4 remain inengagement during each complete cycle of operation of the interrupter as described above. In the illustrated embodiment said means comprises a yoke or band 'ing contact I4 away from contact I2.

4 in the form of a plate 43. having a slot 44 therein. The slot receives reed 20 at one end thereof and a tapered or cam element 45 at the other end, which element may be constrained to move vertically in a straight line. Plate 43 may be suitably supported for movement in a horizontal plane by cam member 45 and, if desired, by resil'ient means (not shown) andreed 20 adapted to yieldably hold the plate toward the left in engagement with said cam element. The right non-vertical edge of member 45 may cooperate with" the end of slot 44 for moving plate 43 but preferably said member has a cam slot 46 through which extends a pin 41 secured to said plate. Downward movement of cam 45, 46 from the position illustrated will accordingly effect movement of slotted plate 43 to the right, thereby flexing reed 20 in the same direction and mov- Thus, when reed I8 bends to the right, the engagement between contacts I2and I4 is delayed an amount determined by the position of cam 45, 46. on the return stroke of reeds I8 and 20,co"n tacts I2 and I4 will disengage when reed 20 is stopped by plate 43 at the left end of slot 44.

Accordingly, the further reed 20 is initially fiex'ed and held to the right by plate 43 and cam 45 the shorter will be the interval of engagement of contacts I2 and I4 without in any way appl e ciably affecting the frequency ofoperation of reed l8 and hence of contacts 32, 33.

In order to control the engagement interval of contacts I2 and I4 in accordance with variations in the available voltage, electromagnetic means responsive to such voltage are provided for actuating cam member 45. As shown, said means comprises a coil 48 through which the lower end of member 45 extends as a movable core. The coil 48 is connected in circuit with battery l0 whenever switch I6 is closed so that a constant downward magnetic pull is exerted upon member 45 against the supporting effort of a spring 49 or other suitable yieldable resistance. This downward pull increases with increased voltage so that when the available voltage is maximum, cam 45, 46 is pulled to its lowermost position, thereby moving plate 43 to the right and decreasing the aforesaid contact engagement interval. The shape of cam 46 may be such that for any given available voltage the contact engagement interval will be just long enough to permit a current of nearly pre-selected magnitude to build up in primary winding 22 or other circuit containing contacts I2 and I4. By thus limiting within a relatively narrow range the maximum current flow inwinding 22 and maintaining the same substantially constant for su'c' cessive cycles, the transformer may be properly designed for attaining the most efficient opena tion under all conditions of operation without danger of the same becoming overheated.

There is thus provided novel electrical circuit means and apparatus-whereby greater efficiency, greater life and greater dependability are assured at less initial cost and with less danger'of interrupted service. -A novel system is provided whereby a reasonably steady electrical output may be assured independently of voltagevariations at the source of power, simplified means being provided for controlling the output in accordance with such-variations. The apparatus comprehended by the invention may be suitably adjusted or calibrated to obtain other ultimate results, such as a variable output bearing a'preselected relation to the variable-input.

Although only a single embodiment of the present invention has been illustrated in diagrammatic form, it is to be expressly understood that the same is not limited thereto. In addition to the variations mentioned in the foregoing description, various other changes may be made, such as in the design and arrangement of parts illustrated, without departing from the spirit and scope of the invention, as will now be understood by those skilled in the art.

What is claimed is:

1. In apparatus of the class described, a source of electrical energy, such as a battery, electrical energy consuming means including a transformer having primary and secondary windings, means including a normally open circuit breaker having a pair of contacts for connecting said primary winding to said source, one of said contacts being adjustable toward and away from the normal position of the other of said contacts, electro-magnetic means for intermittently closing said circuit breaker and releasing the same for return to open position, means connecting said electro-magnetic means in circuit with said source including a pair of normally-closed separable contacts, the latter being separated when said one contact while engaged with said other contact is moved beyond a predetermined position by said electro-magnetic means, to thereby deenergize the latter, means for adjusting the normal position of said one contact in accordance with the output voltage of said source to thereby control the duration of closing of said circuit breaker during each cycle of operation, said last named means including an electromagnet energized by said source and cam means actuated by resilient means and said electromagnet.

2. In apparatus of the class described, an electrical circuit including a source of electrical energy and a normally open circuit breaker for interrupting the circuit, both contacts of said circuit breaker being carried by resilient reeds, a second electrical circuit including a pair of normally engaged separable contacts", electromagnetic means in said second circuit for intermittently moving one of said circuit breaker contacts into engagement with the other and thereafter disengaging said normally engaged contacts for de-energizing said electro-magnetic means, and means responsive to the output voltage of said source for varying the released position of one of said circuit breaker contacts with respect to the other.

3. In apparatus of the class described, a source of electrical energy, an electrical energy consuming circuit including said source and a circuit breaker, means for intermittently opening and closing said circuit breaker to intermittently interrupt said circuit, said means including electro-magnetic means which, while energized, effects and maintains engagement of the circuit breaker contacts, and means for controlling the duration of each closing of said circuit breaker, said control means including electro-magnetL cally actuated cam means.

4. In apparatus of the class described, a source of electrical energy, a device for consuming electrical energy from said source, means including a circuit breaker having a pair of normally disengaged contacts for connecting said device to said source, means including electro-magnctic means for intermittently closing and reopening said circuit breaker to intermittently connect and disconnect said device to and from said source, a pair of normally closed separable contacts in circuit with and separable by said electro-magnetic means to de-energize the latter, the separation of said normally closed contacts being effected during energization of said electromagnetic means after said normally open contacts have been closed and moved beyond a predetermined position by said electro-magnetic means, and means for adjusting the position of on of said normally disengaged contacts relative to the other to vary the engaging period thereof during each cycle of operation in accordance with the output voltage of said source.

5. Apparatus as defined in claim 4 wherein the adjusting means comprises an electro-magnet connected directly across the terminals of said source.

JOHN H. MAYFORTH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 877,258 Thomas Jan. 21, 1908 1,576,236 Czikan Mar. 9, 1926 2,019,328 Thompson Oct. 29, 1935 2,096,276 Garstang Oct. 19, 1937 2,225,335 Dostal Dec. 17, 1940 2,513,608 Weber July 4, 1950 FOREIGN PATENTS Number Country Date 504,773 Germany July 6, 1928 722,209 Germany May 21, 1942 

